Picked up my 2021 m3p 2 weeks ago. Been charging to about 80% or 250 miles. I drive 26 miles on my commute one way and am using 45 miles of battery range.
Conditions: in chill mode not sport, 90% highway DRIVING AT 80. 48 degrees F outside.
Is it normal to lose this much charge?
As mentioned, yes perfectly normal at the speed I bolded in your quote above.